Influence of Fluid Motion on Blue Green Algae: Microcystis aeruginosa

Shahram Missaghi, associate extension professor, UMN extension, University of Minnesota

Algae blooms can turn the water green and smelly, contribute to fish kills, and may produce toxins that pose a health risk to people and animals. These types of algae blooms are referred to as Harmful Algal Blooms or HABs.   Microcystis aeruginosa (Microcystis) under suitable conditions may rapidly grow and reach extremely high cell concentrations (bloom) in just a few days. Microcystis HABs are on the rise globally, and there is an urgent need to understand and identify the forcing factors that influence Microcystis growth and bloom.  

We hypothesized that fluid motion has an influence on the growth and the vertical variability of Microcystis, and its influence can be quantified by measuring the corresponding rate of energy dissipation levels of fluid motion.  In this presentation, I will share how we conducted laboratory experiment measuring the population growth and vertical distribution of Microcystis in a bioreactor.  We also measure fluid velocities using a two-dimensional particle image velocimetry.  Our results showed that Microcystis growth rate and vertical heterogeneity were coupled.  The results will be instrumental in developing mechanistic models of the spatial and temporal distribution of Microcystis that can improve management of aquatic ecosystems.